>blame EPA regulations To elaborate, since I've even had to explain this to some "eco-conscious" engineers: This is also partially why trucks have gone from s

>blame EPA regulations To elaborate, since I've even had to explain this to some "eco-conscious" engineers: This is also partially why trucks have gone from steel to aluminum, which is lighter (to gain a marginal increase in mpg), but also requires larger shapes (moment-arms) to achieve the same amount of strength and resilience (crumple zone rigidity & required crumple zone size, etc). Of course the other side effect is that using aluminum frames/engines won't last as long, since they deform easier, so all that saved energy from increased mpg doesn't make up for the wasted embedded energy from decreased useful lifespan.